The Aztec or Mexica calendar is the calendar system, used by the Aztecs as well as other Pre-Columbian peoples of central Mexico. It is one of the Mesoamerican calendars, sharing the basic structure of calendars from throughout ancient Mesoamerica; the Aztec calendar stone called the Sun Stone, is on display at the National Museum of Anthropology in Mexico City. The calendar consisted of a 365-day calendar cycle called xiuhpōhualli and a 260-day ritual cycle called tōnalpōhualli; these two cycles together formed a 52-year "century", sometimes called the "calendar round". The xiuhpōhualli is considered to be the agricultural calendar, since it is based on the sun, the tōnalpōhualli is considered to be the sacred calendar; the tōnalpōhualli consists of a cycle of 260 days, each day signified by a combination of a number from 1 to 13, one of the twenty day signs. With each new day, both the number and day sign would be incremented: 1 Crocodile is followed by 2 Wind, 3 House, 4 Lizard, so forth up to 13 Reed, after which the cycle of numbers would restart resulting in 1 Jaguar, 2 Eagle, so on, as the days following 13 Reed.

This cycle of number and day signs would continue until the 20th week, which would start on 1 Rabbit, end on 13 Flower. It would take a full 260 days for the two cycles to realign and repeat the sequence back on 1 Crocodile; the set of day signs used in central Mexico is identical to that used by Mixtecs, to a lesser degree similar to those of other Mesoamerican calendars. Each of the day signs bears an association with one of the four cardinal directions. There is some variation in the way the day signs were carved; those here were taken from the Codex Magliabechiano. Wind and Rain are represented by images of Ehēcatl and Tlāloc respectively. Other marks on the stone showed the current world and the worlds before this one; each world was called a sun, each sun had its own species of inhabitants. The Aztecs believed that they were in the Fifth Sun and like all of the suns before them they would eventually perish due to their own imperfections; every 52 years was marked out because they believed that 52 years was a life cycle and at the end of any given life cycle the gods could take away all that they have and destroy the world.

The 260 days of the sacred calendar were grouped into twenty periods of 13 days each. Scholars refer to these thirteen-day "weeks" as trecenas, using a Spanish term derived from trece "thirteen"; the original Nahuatl term is not known. Each trecena is named according to the calendar date of the first day of the 13 days in that trecena. In addition, each of the twenty trecenas in the 260-day cycle had its own tutelary deity: In ancient times the year was composed of eighteen months, thus it was observed by the native people. Since their months were made of no more than twenty days, these were all the days contained in a month, because they were not guided by the moon but by the days; the days of the year were counted twenty by twenty. Xiuhpōhualli is the Aztec year count. One year consists of 5 nameless. These'extra' days are thought to be unlucky; the year was broken into 18 periods of twenty days each, sometimes compared to the Julian month. The Nahuatl word for moon is metztli but whatever name was used for these periods is unknown.

Through Spanish usage, the 20-day period of the Aztec calendar has become known as a veintena. Each 20-day period started on Cipactli; the eighteen veintena are listed below. The dates are from early eyewitnesses. Bernardino de Sahagún's date precedes the observations of Diego Durán by several decades and is believed to be more recent to the surrender. Both are shown to emphasize the fact that the beginning of the Native new year became non-uniform as a result of an absence of the unifying force of Tenochtitlan after the Mexica defeat; the ancient Mexicans counted their years by means of four signs combined with thirteen numbers, obtaining periods of 52 years, which are known as Xiuhmolpilli, a popular but incorrect name. We can see below the table with the current years: For many centuries scholars had tried to reconstruct the Calendar; the latest and more accepted version was proposed by Professor Rafael Tena of the Instituto Nacional de Antropología e Historia, based on the studies of Sahagún and Alfonso Caso of the National Autonomous University of Mexico.

His correlation confirms that the first day of the Mexica year was February 13 of the old Julian calendar or February 23 of the current Gregorian calendar. Using the same count, it has been verified the date of the birth of Huitzilopochtli, the end of the year and a cycle or "Tie of the Years", the New Fire Ceremony, day-sign 1 Tecpatl of the year 2 Acatl, corresponding to the date February 22. Maya calendar Mesoamerican calendars Aztec New YearMuisca calendar The Aztec Calendar - Ancient History Encyclopedia Detailed description of the temalacatl from Mexico's Museo Nacional de Antropología Daily Aztec Calendar Aztec Calendar Ruben Ochoa Correlation

A wordfilter is a script used on Internet forums or chat rooms that automatically scans users' posts or comments as they are submitted and automatically changes or censors particular words or phrases. The most basic wordfilters search only for specific strings of letters, remove or overwrite them regardless of their context. More advanced wordfilters make some exceptions for context, the most advanced wordfilters may use regular expressions. Wordfilters can serve any of a number of functions. A swear filter known as a profanity filter or language filter is a software subsystem which modifies text to remove words deemed offensive by the administrator or community of an online forum. Swear filters are common in custom-programmed chat rooms and online video games MMORPGs; this is not to be confused with content filtering, built into internet browsing programs by third-party developers to filter or block specific websites or types of websites. Swear filters are created or implemented by the developers of the Internet service.

Most wordfilters are used to censor language considered inappropriate by the operators of the forum or chat room. Expletives are partially replaced replaced, or replaced by nonsense words; this relieves the administrators or moderators of the task of patrolling the board to watch for such language. This may help the message board avoid content-control software installed on users' computers or networks, since such software blocks access to Web pages that contain vulgar language. Filtered phrases may be permanently replaced as it is saved, or the original phrase may be saved but displayed as the censored text. In some software users can view the text behind the wordfilter by quoting the post. Swear filters take advantage of string replacement functions built into the programming language used to create the program, to swap out a list of inappropriate words and phrases with a variety of alternatives. Alternatives can include: grawlix nonsense characters, such as!@#$%^&* Replacing a certain letter with a shift-number character or a similar looking one.

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Internet forums are sometimes attacked by vandals who try to fill the forum with repeated nonsense messages, or by spammers who try to insert links to their commercial web sites. The site's wordfilter may be configured to remove the nonsense text used by the vandals, or to remove all links to particular websites from posts. Lameness filters are text-based wordfilters used by Slash-based websites to stop junk comments from being posted in response to stories; some of the things they are designed to filter include: Too many capital letters Too much repetition ASCII art Comments which are too short or long Use of HTML tags that try to break web pages Comment titles consisting of "first post" Any occurrence of a word or term deemed to be offensive/vulgar Since wordfilters are automated and look only for particular sequences of characters, users aware of the filters will sometimes try to circumvent them by changing their lettering just enough to avoid the filters. A user trying to avoid a vulgarity filter might replace one of the characters in the offending word into an asterisk, dash, or something similar.

Some administrators respond by revising the wordfilters to catch common substitutions. A simple example of evading a wordfilter would be using leet. More advanced techniques of wordfilter evasion include the use of images, using hidden tags, or Cyrillic characters. Another method is to use a soft hyphen. A soft hyphen is only used to indicate where a word can be split when breaking text lines and is not displayed. By placing this halfway in a word, the word gets broken up and will in some cases not be recognised by the wordfilter; some more advanced filters, such as those in the online game RuneScape, can detect bypassing. However, the downside of sensitive wordfilters is. Wordfilters are coded into the Internet forums or chat rooms, operate only on material submitted to the forum or chat room in question; this distinguishes wordfilters from content-control software, installed on an end user's PC or computer network, which can filter all Internet content sent to or from the PC or network in question.